Android builders often brush a irritating script: a Position’s getWidth() and getHeight() strategies instrument zero, equal last the structure seemingly completes. This perplexing content tin pb to incorrect calculations, misaligned UI parts, and a mostly breached person education. Knowing the underlying causes and using effectual options is important for gathering sturdy and visually interesting Android purposes.
Wherefore getWidth() and getHeight() Instrument zero
The capital ground these strategies instrument zero is that the Position’s dimensions haven’t been calculated but. Android’s structure procedure is asynchronous. Calling these strategies instantly last mounting the contented position oregon throughout onCreate() volition frequently output zero values due to the fact that the format walk hasn’t completed. The scheme wants clip to measurement and assumption all Position inside the format hierarchy.
Another contributing components tin see analyzable nested layouts, customized Views with incorrect measure logic, and circumstantial instrumentality configurations. Debugging this content requires a methodical attack and an knowing of the structure lifecycle.
Options for Retrieving Close Dimensions
Respective methods be for acquiring close Position dimensions. 1 communal attack is utilizing the ViewTreeObserver. This people permits you to registry a listener that will get notified once the Position’s structure is absolute. Wrong the onGlobalLayout() callback, you tin safely retrieve the width and tallness.
- Connect a
ViewTreeObserver.OnGlobalLayoutListenerto your Position. - Override the
onGlobalLayout()methodology. - Wrong
onGlobalLayout(), callgetWidth()andgetHeight(). - Distance the listener to forestall aggregate calls (crucial!).
Different effectual technique is utilizing the station() technique of the Position. This schedules a Runnable to beryllium executed last the structure walk. Wrong the Runnable, the dimensions volition beryllium disposable.
Leveraging LayoutParams
Typically, knowing the LayoutParams related with a Position tin aid diagnose the content. Incorrectly configured LayoutParams tin pb to surprising dimensions. For case, mounting the width oregon tallness to WRAP_CONTENT once a fastened dimension is wanted tin origin issues. Analyzing the LayoutParams successful the debugger tin uncover specified inconsistencies.
See these factors once running with LayoutParams:
- Guarantee the accurate
LayoutParamskind is utilized for the genitor ViewGroup. - Confirm the width and tallness settings inside the
LayoutParams.
Champion Practices for Dealing with Position Dimensions
Proactively addressing possible magnitude points tin prevention debugging clip. Using a strong structure plan, avoiding profoundly nested hierarchies, and completely investigating connected assorted surface sizes and orientations tin decrease the chance of encountering this job.
Present are any additional champion practices:
- Usage ConstraintLayout for analyzable layouts to optimize show and trim nesting.
- Cautiously see the usage of
WRAP_CONTENTandMATCH_PARENT.
Arsenic Robert Martin, writer of “Cleanable Codification,” states, “The lone manner to spell accelerated is to spell fine.” Investing clip successful appropriate structure plan and magnitude dealing with finally leads to cleaner, much maintainable codification.
[Infographic placeholder: illustrating the format lifecycle and however dimensions are calculated]
In accordance to Stack Overflow’s 2022 Developer Study, Android improvement stays a extremely fashionable country. Knowing format intricacies is a important accomplishment for immoderate Android developer. Larn much astir structure champion practices.
FAQ
Q: Wherefore does getMeasuredWidth() typically instrument a antithetic worth than getWidth()?
A: getMeasuredWidth() represents the Position’s desired width last the measure walk, piece getWidth() represents the last width last the format walk. Variations tin originate owed to constraints imposed by the genitor ViewGroup.
By knowing the Android structure lifecycle and utilizing the strategies outlined supra, you tin efficaciously grip conditions wherever getWidth() and getHeight() instrument zero, starring to much sturdy and dependable Android functions. Retrieve to choice the about due methodology for your circumstantial script and prioritize a cleanable, fine-structured structure plan. This proactive attack volition not lone lick the contiguous content however besides lend to a amended general improvement education. Research assets similar the authoritative Android documentation and Stack Overflow for additional insights and assemblage activity. Dive deeper into knowing Position measure and format passes to fortify your Android improvement expertise.
Android ViewTreeObserver Documentation
Question & Answer :
I americium creating each of the parts successful my android task dynamically. I americium making an attempt to acquire the width and tallness of a fastener truthful that I tin rotate that fastener about. I americium conscionable making an attempt to larn however to activity with the android communication. Nevertheless, it returns zero.
I did any investigation and I noticed that it wants to beryllium carried out location another than successful the onCreate() methodology. If person tin springiness maine an illustration of however to bash it, that would beryllium large.
Present is my actual codification:
bundle com.animation; import android.app.Act; import android.os.Bundle; import android.position.animation.Animation; import android.position.animation.LinearInterpolator; import android.position.animation.RotateAnimation; import android.widget.Fastener; import android.widget.LinearLayout; national people AnimateScreen extends Act { //Referred to as once the act is archetypal created. @Override national void onCreate(Bundle savedInstanceState) { ace.onCreate(savedInstanceState); LinearLayout ll = fresh LinearLayout(this); LinearLayout.LayoutParams layoutParams = fresh LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT); layoutParams.setMargins(30, 20, 30, zero); Fastener bt = fresh Fastener(this); bt.setText(Drawstring.valueOf(bt.getWidth())); RotateAnimation ra = fresh RotateAnimation(zero,360,bt.getWidth() / 2,bt.getHeight() / 2); ra.setDuration(3000L); ra.setRepeatMode(Animation.RESTART); ra.setRepeatCount(Animation.INFINITE); ra.setInterpolator(fresh LinearInterpolator()); bt.startAnimation(ra); ll.addView(bt,layoutParams); setContentView(ll); }
The basal job is, that you person to delay for the drafting form for the existent measurements (particularly with dynamic values similar wrap_content oregon match_parent), however normally this form hasn’t been completed ahead to onResume(). Truthful you demand a workaround for ready for this form. Location are antithetic imaginable options to this:
- Perceive to Gully/Structure Occasions: ViewTreeObserver
A ViewTreeObserver will get fired for antithetic drafting occasions. Normally the OnGlobalLayoutListener is what you privation for getting the measure, truthful the codification successful the listener volition beryllium referred to as last the format form, truthful the measurements are fit:
position.getViewTreeObserver().addOnGlobalLayoutListener(fresh ViewTreeObserver.OnGlobalLayoutListener() { @Override national void onGlobalLayout() { position.getViewTreeObserver().removeOnGlobalLayoutListener(this); position.getHeight(); //tallness is fit } });
Line: The listener volition beryllium instantly eliminated due to the fact that other it volition occurrence connected all format case. If you person to activity apps SDK Flat < sixteen usage this to unregister the listener:
national void removeGlobalOnLayoutListener (ViewTreeObserver.OnGlobalLayoutListener unfortunate)
- Adhd a runnable to the structure queue: Position.station()
Not precise fine identified and my favorite resolution. Fundamentally conscionable usage the Position’s station methodology with your ain runnable. This fundamentally queues your codification last the position’s measurement, structure, and so on. arsenic said by Romain Cat:
The UI case queue volition procedure occasions successful command. Last setContentView() is invoked, the case queue volition incorporate a communication asking for a relayout, truthful thing you station to the queue volition hap last the structure walk
Illustration:
last Position position=...; ... position.station(fresh Runnable() { @Override national void tally() { position.getHeight(); //tallness is fit } });
Brand certain that this runnable runs connected the UI thread, other this mightiness not activity.
The vantage complete ViewTreeObserver:
- your codification is lone executed erstwhile, and you don’t person to disable the Perceiver last execution which tin beryllium a trouble
- little verbose syntax
References:
three. Overwrite Views’s onLayout Methodology
This is lone applicable successful definite occupation once the logic tin beryllium encapsulated successful the position itself, other this is a rather verbose and cumbersome syntax.
position = fresh Position(this) { @Override protected void onLayout(boolean modified, int l, int t, int r, int b) { ace.onLayout(modified, l, t, r, b); position.getHeight(); //tallness is fit } };
Besides head, that onLayout volition beryllium known as galore occasions, truthful beryllium thoughtful what you bash successful the methodology, oregon disable your codification last the archetypal clip
four. Cheque if has been done format form
If you person codification that is executing aggregate instances piece creating the UI you may usage the pursuing activity v4 lib technique:
Position viewYouNeedHeightFrom = ... ... if(ViewCompat.isLaidOut(viewYouNeedHeightFrom)) { viewYouNeedHeightFrom.getHeight(); }
Returns actual if position has been done astatine slightest 1 format since it was past hooked up to oregon indifferent from a framework.
Further: Getting statically outlined measurements
If it suffices to conscionable acquire the statically outlined tallness/width, you tin conscionable bash this with:
However head you, that this mightiness beryllium antithetic to the existent width/tallness last drafting. The Javadoc describes the quality successful much item:
The dimension of a position is expressed with a width and a tallness. A position really have 2 pairs of width and tallness values.
The archetypal brace is identified arsenic measured width and measured tallness. These dimensions specify however large a position needs to beryllium inside its genitor (seat Format for much particulars.) The measured dimensions tin beryllium obtained by calling getMeasuredWidth() and getMeasuredHeight().
The 2nd brace is merely identified arsenic width and tallness, oregon typically drafting width and drafting tallness. These dimensions specify the existent dimension of the position connected surface, astatine drafting clip and last format. These values whitethorn, however bash not person to, beryllium antithetic from the measured width and tallness. The width and tallness tin beryllium obtained by calling getWidth() and getHeight().
